This week's rise in fuel prices is a blessing in disguise for Guangzhou's efforts to clean up its air - it is hastening the conversion of bus and taxi fleets to run on liquefied petroleum gas.

The target for full fleet conversion is the end of the year, but drivers have noticed a rise in LPG users since petrol prices were raised for the first time this year in March.

'It used to take 15 minutes at peak hours to fill up, but since the Lunar New Year holiday it's taking me an hour. There are many more taxis and buses in the queue,' said taxi driver Lui Shufang, who has been driving an LPG-powered Volkswagen Jetta for two years.

'It's become so inconvenient and the savings were not that much so I converted back to petrol two days ago ... It was the same day they announced the price increase. I didn't know they were going to raise prices and I regretted my decision because I wasted several hundred yuan,' he said.

Mr Lui is reconverting his engine to burn LPG because its price is lower and the switch back will put 700 yuan a month back into his and his partner's pockets from the surcharge of 1 yuan per trip they are allowed to collect.

The partners had been willing to give up the income from the surcharge to avoid the long queues at the few gas stations, which are situated in remote locations.

A spokesman at one taxi company said its fleet of taxis had been converted to gas.

'If we don't use LPG, our costs would go up 8 to 10 per cent. At the moment there is no impact, but if prices continue to go up there will be a problem,' he said.

The price of petrol at the pump rose 9.6 per cent and the price of diesel 11 per cent this week - the second rise since March.

The Guangdong Oil and Gas Association predicts petrol prices will rise another 17 per cent, to 6 yuan a litre, by the end of the year as mainland oil prices gradually catch up with world prices.

The Guangzhou government has spent 100 million yuan converting vehicles to gas and will spend another 50 million yuan to complete the scheme this year.

'At the beginning, we were looking at the conversion from an environmental conservation point of view, but now we find that it is helping to slow down the rise in oil prices,' a transport commission official said.

Guangzhou has 16,000 taxis, of which 70 per cent have already switched to LPG, while 74 per cent of its 6,000 buses also run on LPG.